The present invention relates to the production of light-weight molded articles from aqueous dispersions containing ceramic fibers, finely divided refractory materials and conventional additives.
Light-weight molded articles which contain a ceramic fiber component are used for purposes of insulation and as coatings which come into contact with molten metal, especially melts of aluminum and aluminum alloys.
For example, DE-AS 19 47 904 describes a refractory, heat-insulating material of aluminum silicate fibers and a bonding agent, which includes refractory filler materials in particle form. This known heat-insulating material is produced from an aqueous suspension with a consistency of 1% which is formed by dewatering the suspension in screen molds. The refractory material contains starch as bonding agent and a colloidal silicon dioxide sol.
European patent application No. 0 077 444 discloses a plate material containing a small portion of ceramic fibers, an organic bonding agent and colloidal silicon dioxide as inorganic bonding agent, as well as small quantities of a flocculating agent. This plate material contains more than 50% by weight of an inorganic fire-resistant filler material. In the production of such plates, a cationic polyacrylamide is used as a flocculating agent, which is added as a last component to the aqueous suspension of the other components.
A refractory insulation material and method for its production is also known from German Patent Application 1 646 449, which consists of 2 to 10% by weight aluminum-silicate fibers, very finely divided silicon dioxide and calcium aluminate bonding agents and 32 to 68% water, relative to the dry weight of the mixture.